#region License
// Copyright (c) Jeremy Skinner (http://www.jeremyskinner.co.uk)
// 
// Licensed under the Apache License, Version 2.0 (the "License"); 
// you may not use this file except in compliance with the License. 
// You may obtain a copy of the License at 
// 
// http://www.apache.org/licenses/LICENSE-2.0 
// 
// Unless required by applicable law or agreed to in writing, software 
// distributed under the License is distributed on an "AS IS" BASIS, 
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
// See the License for the specific language governing permissions and 
// limitations under the License.
// 
// The latest version of this file can be found at http://www.codeplex.com/FluentValidation
#endregion

namespace ServiceStack.FluentValidation.Resources
{
    using System;
    using System.Linq.Expressions;
    using System.Reflection;
    using Internal;

    /// <summary>
    /// Represents a localized string.
    /// </summary>
    public class LocalizedStringSource : IStringSource {
        readonly Func<string> accessor;
        readonly Type resourceType;
        readonly string resourceName;

        /// <summary>
        /// Creates a new instance of the LocalizedErrorMessageSource class using the specified resource name and resource type.
        /// </summary>
        /// <param name="resourceType">The resource type</param>
        /// <param name="resourceName">The resource name</param>
        /// <param name="resourceAccessorBuilder">Strategy used to construct the resource accessor</param>
        public LocalizedStringSource(Type resourceType, string resourceName, IResourceAccessorBuilder resourceAccessorBuilder) {
            this.resourceType = resourceType;
            this.resourceName = resourceName;
            this.accessor = resourceAccessorBuilder.GetResourceAccessor(resourceType, resourceName);
        }

        /// <summary>
        /// Creates an IErrorMessageSource from an expression: () => MyResources.SomeResourceName
        /// </summary>
        /// <param name="expression">The expression </param>
        /// <param name="resourceProviderSelectionStrategy">Strategy used to construct the resource accessor</param>
        /// <returns>Error message source</returns>
        public static IStringSource CreateFromExpression(Expression<Func<string>> expression, IResourceAccessorBuilder resourceProviderSelectionStrategy) {
            var constant = expression.Body as ConstantExpression;

            if (constant != null) {
                return new StaticStringSource((string)constant.Value);
            }

            var member = expression.GetMember();

            if (member == null) {
                throw new InvalidOperationException("Only MemberExpressions an be passed to BuildResourceAccessor, eg () => Messages.MyResource");
            }

            var resourceType = member.DeclaringType;
            var resourceName = member.Name;
            return new LocalizedStringSource(resourceType, resourceName, resourceProviderSelectionStrategy);
        }

        /// <summary>
        /// Construct the error message template
        /// </summary>
        /// <returns>Error message template</returns>
        public string GetString() {
            return accessor();
        }

        /// <summary>
        /// The name of the resource if localized.
        /// </summary>
        public string ResourceName {
            get { return resourceName; }
        }

        /// <summary>
        /// The type of the resource provider if localized.
        /// </summary>
        public Type ResourceType {
            get { return resourceType; }
        }
    }
}